Method for reforming amorphous carbon polymer film

ABSTRACT

A method for reforming an amorphous carbon film as part of a deposition process thereof, includes process of: (i) depositing an amorphous carbon film on a substrate in a reaction space until a thickness of the amorphous carbon film reaches a predetermined thickness, and then stopping the deposition process; and (ii) exposing the amorphous carbon film to an Ar and/or He plasma in an atmosphere substantially devoid of hydrogen, oxygen, and nitrogen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/844,705 filed on May 7, 2019, the disclosure of whichis incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to a method for reforming anamorphous carbon polymer film, particularly, with respect to thermalstability.

Description of the Related Art

In processes of fabricating integrated circuits such as those forshallow trench isolation, inter-metal dielectric layers, passivationlayers, etc., it is often necessary to fill trenches (any recesstypically having an aspect ratio of one or higher) with insulatingmaterial. However, with miniaturization of wiring pitch of large scaleintegration (LSI) devices, void-free filling of high aspect ratio spaces(e.g., AR≥3) becomes increasingly difficult due to limitations ofexisting deposition processes.

Further, in order to densify deposited films, repair damage from ionbombardment, and/or improve chemical/physical properties, annealing of adeposited film is often performed. In this disclosure, “annealing”refers to a process applied to a film having a film matrix alreadyformed, during which a film/layer is treated to be changed to its stableform, e.g., to change a terminal group to a more stable group (e.g.,removal of hydrogen-containing terminals), which is distinguished from“curing” which is a process applied to a layer to form a film matrix.

Although an amorphous carbon polymer film is useful in gap-filltechnology and/or in patterning as, e.g., a hardmask, a conventionalamorphous carbon polymer typically has a high thermal shrinkage. Whensignificant shrinkage occurs, an amorphous carbon polymer film is likelyto be detached from a contacting surface and/or to undergo adeterioration its properties.

In view of the conventional gap-fill technology and/or patterningtechnology, an embodiment of the present invention which, however, isnot limited thereto provides a method of forming an amorphous carbonpolymer film having high thermal stability.

Any discussion of problems and solutions involved in the related art hasbeen included in this disclosure solely for the purposes of providing acontext for the present invention, and should not be taken as anadmission that any or all of the discussion were known at the time theinvention was made.

When an amorphous carbon polymer film is formed by using aplasma-assisted method, the resultant amorphous carbon polymer film isconstituted by hydrogenated amorphous carbon polymer. In thisdisclosure, a hydrogenated amorphous carbon polymer may simply bereferred to an amorphous carbon polymer, which may also be referred toas “aC:H” or simply “aC” as an abbreviation. Further, in thisdisclosure, SiC, SiCO, SiCN, SiCON, or the like is an abbreviationindicating a film type (indicated simply by primary constituentelements) in a non-stoichiometric manner unless described otherwise.

SUMMARY OF THE INVENTION

In some embodiments, a method for reforming an amorphous carbon polymerfilm as part of a deposition process thereof, comprises process of: (i)depositing an amorphous carbon polymer film on a substrate in a reactionspace until a thickness of the amorphous carbon polymer film reaches apredetermined thickness, and then stopping the deposition process; and(ii) exposing the amorphous carbon polymer film to an Ar and/or Heplasma in an atmosphere substantially devoid of hydrogen, oxygen, andnitrogen. Accordingly, thermal stability of the amorphous carbon polymerfilm can significantly be improved. The “atmosphere substantially devoidof hydrogen, oxygen, and nitrogen” refers to no gas containing hydrogen,oxygen, or nitrogen being fed to the reaction space wherein a residualgas and/or gas released from a film which may contain hydrogen, oxygen,and/or nitrogen may be present as impurities or immaterial components.In some embodiments, in process (ii), solely Ar and/or He gas innon-excited state are/is fed to the reaction space and excited by RFpower applied to electrodes, e.g., capacitively-coupled flat electrodes,provided in the reaction space, or solely Ar and/or He gas in an excitedstate are/is fed to the reaction space.

In some embodiments, process (ii) is cyclically conducted after every 1nm to 15 nm of film growth in process (i).

For purposes of summarizing aspects of the invention and the advantagesachieved over the related art, certain objects and advantages of theinvention are described in this disclosure. Of course, it is to beunderstood that not necessarily all such objects or advantages may beachieved in accordance with any particular embodiment of the invention.Thus, for example, those skilled in the art will recognize that theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

Further aspects, features and advantages of this invention will becomeapparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described withreference to the drawings of preferred embodiments which are intended toillustrate and not to limit the invention. The drawings are greatlysimplified for illustrative purposes and are not necessarily to scale.

FIG. 1A is a schematic representation of a PEALD (plasma-enhanced atomiclayer deposition) apparatus for depositing a dielectric film usable inan embodiment of the present invention.

FIG. 1B illustrates a schematic representation of a precursor supplysystem using a flow-pass system (FPS) usable in an embodiment of thepresent invention.

FIG. 2 is a graph showing shrinkage of amorphous carbon polymer filmswithout plasma treatment (“STD”), with Ar plasma treatment (“Ar”), andwith He plasma treatment (“He”) after annealing under differentconditions, wherein “Ar” and “He” represent embodiments of the presentinvention.

FIG. 3 shows Fourier Transform Infrared (FTIR) spectrums of amorphouscarbon polymer films without plasma treatment (“STD”), with Ar plasmatreatment (“Ar”), and with He plasma treatment (“He”), wherein “Ar” and“He” represent embodiments of the present invention.

FIG. 4 shows a STEM photograph of a cross-sectional view of trenchessubjected to a gap-fill process with He plasma treatment according to anembodiment of the present invention, wherein arrows show slightly darkerinterfaces indicative of He plasma treatment.

FIG. 5 is a chart illustrating the sequence of processes of filmformation according to an embodiment of the present invention, wherein acell in gray represents an ON state whereas a cell in white representsan OFF state, and the width of each column does not represent durationof each process.

DETAILED DESCRIPTION OF EMBODIMENTS

In this disclosure, “gas” may include vaporized solid and/or liquid andmay be constituted by a single gas or a mixture of gases, depending onthe context. Likewise, an article “a” or “an” refers to a species or agenus including multiple species, depending on the context. In thisdisclosure, a process gas introduced to a reaction chamber through ashowerhead may be comprised of, consist essentially of, or consist of asilicon-free hydrocarbon precursor and an additive gas. The additive gasmay include a plasma-generating gas for exciting the precursor to forman amorphous carbon polymer when RF power is applied to the additivegas. The additive gas may be an inert gas which may be fed to a reactionchamber as a carrier gas and/or a dilution gas. The additive gas maycontain no reactant gas for oxidizing or nitriding the precursor.Alternatively, the additive gas may contain a reactant gas for oxidizingor nitriding the precursor to the extent not interfering with plasmapolymerization forming an amorphous carbon-based polymer. Further, insome embodiments, the additive gas contains only a plasma-generating gas(e.g., noble gas). The precursor and the additive gas can be introducedas a mixed gas or separately to a reaction space. The precursor can beintroduced with a carrier gas such as a rare gas. A gas other than theprocess gas, i.e., a gas introduced without passing through theshowerhead, may be used for, e.g., sealing the reaction space, whichincludes a seal gas such as a rare gas. In some embodiments, the term“precursor” refers generally to a compound that participates in thechemical reaction that produces another compound, and particularly to acompound that constitutes a film matrix or a main skeleton of a film,whereas the term “reactant” refers to a compound, other than precursors,that activates a precursor, modifies a precursor, or catalyzes areaction of a precursor, wherein the reactant may provide an element(such as O, C, N) to a film matrix and become a part of the film matrix,when in an excited state. The term “plasma-generating gas” refers to acompound, other than precursors and reactants, that generates a plasmawhen being exposed to electromagnetic energy, wherein theplasma-generating gas may not provide an element (such as O, C, N) to afilm matrix which becomes a part of the film matrix. The term “reforminggas” refers to a gas which reforms a film already deposited, when in anexcited state, typically without further growing the film (without anyprecursor). In some embodiments, the “reforming gas” is aplasma-generating gas.

In some embodiments, “film” refers to a layer continuously extending ina direction perpendicular to a thickness direction substantially withoutpinholes to cover an entire target or concerned surface, or simply alayer covering a target or concerned surface. In some embodiments,“layer” refers to a structure having a certain thickness formed on asurface or a synonym of film or a non-film structure. A film or layermay be constituted by a discrete single film or layer having certaincharacteristics or multiple films or layers, and a boundary betweenadjacent films or layers may or may not be clear and may be establishedbased on physical, chemical, and/or any other characteristics, formationprocesses or sequence, and/or functions or purposes of the adjacentfilms or layers. Further, in this disclosure, any two numbers of avariable can constitute a workable range of the variable as the workablerange can be determined based on routine work, and any ranges indicatedmay include or exclude the endpoints. Additionally, any values ofvariables indicated (regardless of whether they are indicated with“about” or not) may refer to precise values or approximate values andinclude equivalents, and may refer to average, median, representative,majority, etc. in some embodiments. Further, in this disclosure, theterms “constituted by” and “having” refer independently to “typically orbroadly comprising”, “comprising”, “consisting essentially of”, or“consisting of” in some embodiments. In this disclosure, any definedmeanings do not necessarily exclude ordinary and customary meanings insome embodiments.

In this disclosure, “continuously” refers to without breaking a vacuum,without interruption as a timeline, without any material interveningstep, without changing treatment conditions, immediately thereafter, asa next step, or without an intervening discrete physical or chemicalstructure between two structures other than the two structures in someembodiments.

In this disclosure, a “recess or step” refers to any structure having atop surface, a sidewall, and a bottom surface formed on a substrate,which may continuously be arranged in series in a height direction ormay be a single recess or step, and which may constitute a trench, a viahole, or other recesses. In this disclosure, a recess between adjacentprotruding structures and any other recess pattern is referred to as a“trench”. That is, a trench is any recess pattern including a hole/viaand which has, in some embodiments, a width of about 20 nm to about 100nm (typically about 30 nm to about 50 nm) (wherein when the trench has alength substantially the same as the width, it is referred to as ahole/via, and a diameter thereof is about 20 nm to about 100 nm), adepth of about 30 nm to about 100 nm (typically about 40 nm to about 60nm), and an aspect ratio of about 2 to about 10 (typically about 2 toabout 5). The proper dimensions of the trench may vary depending on theprocess conditions, film compositions, intended applications, etc.

In some embodiments, a method for reforming an amorphous carbon polymerfilm as part of a deposition process thereof, comprises two processes:(i) depositing an amorphous carbon polymer film on a substrate in areaction space until a thickness of the amorphous carbon polymer filmreaches a predetermined thickness, and then stopping the depositionprocess; and (ii) exposing the amorphous carbon polymer film to an Arand/or He plasma in an atmosphere substantially devoid of hydrogen,oxygen, and nitrogen.

In some embodiments, the amorphous carbon polymer film is a flowablefilm, and in other embodiments, the amorphous carbon polymer film is anon-flowable film.

Deposition of flowable film is known in the art; however, conventionaldeposition of flowable film uses chemical vapor deposition (CVD) withconstant application of RF power, since pulse plasma-assisted depositionsuch as PEALD is well known for depositing a conformal film which is afilm having characteristics entirely opposite to those of flowable film.In some embodiments, flowable film is a silicon-free carbon-containingfilm constituted by an amorphous carbon polymer, and although anysuitable one or more of hydrocarbon precursors can be candidates, insome embodiments, the precursor includes an unsaturated or cyclichydrocarbon having a vapor pressure of 1,000 Pa or higher at 25° C. Insome embodiments, the precursor is at least one selected from the groupconsisting of C2-C8 alkynes (C_(n)H_(2n-2)), C2-C8 alkenes(C_(n)H_(2n)), C2-C8 diene (C_(n)H_(n+2)), C3-C8 cycloalkenes, C3-C8annulenes (C_(n)H_(n)), C3-C8 cycloalkanes, and substituted hydrocarbonsof the foregoing. In some embodiments, the precursor is ethylene,acetylene, propene, butadiene, pentene, cyclopentene, benzene, styrene,toluene, cyclohexene, and/or cyclohexane.

In some embodiments, as the gap-fill technology for deposition offlowable film, the method disclosed in U.S. patent application Ser. No.16/026,711 can be used, which provides complete gap-filling byplasma-assisted deposition using a hydrocarbon precursor substantiallywithout formation of voids under conditions where a nitrogen, oxygen, orhydrogen plasma is not required, the disclosure of which is hereinincorporated by reference in its entirety.

By changing deposition conditions or process parameters, a non-flowablefilm can be formed. For example, such parameters include, but are notlimited to, partial pressure of precursor, deposition temperature,deposition pressure, etc. For example, by increasing the depositiontemperature, decreasing the deposition pressure, and/or decreasing theprecursor ratio (a ratio of precursor flow to carrier/dilution gasflow), the flowability of film becomes low. In some embodiments, process(i) (deposition process) is conducted by plasma-enhanced atomic layerdeposition (PEALD) or other cyclic plasma-assisted deposition (e.g.,cyclic PECVD). As a plasma, a capacitively coupled plasma, inductivelycoupled plasma, remote plasma, a plasma generated by RF power, a plasmagenerated by microwaves, etc. can be used.

In some embodiments, when the thickness of deposited film in process (i)(deposition process) reaches a monolayer thickness or more but 15 nm orless, preferably 10 nm or less, more preferably 5 nm or less, thedeposition process is stopped, followed by process (ii) (reformationprocess). As the film thickness increases prior to process (ii) (afterthe previous process (ii) if any), the overall reforming effectdecreases. If the film thickness is larger than a maximum depth whichthe reforming effect by the treatment can be obtained, filmquality/properties in a depth/thickness direction become inhomogeneous.If the film thickness is sufficiently small for receiving the reformingeffect by the treatment, film quality/properties in the depth/thicknessdirection become homogeneous, thereby uniformly suppressing shrinkage ofthe film when subjected to subsequent annealing or other high thermalbudget processes at, e.g., 200° C. to 400° C.

In some embodiments, processes (i) and (ii) are repeated multiple timesuntil a thickness of the amorphous silicon film reaches a desired finalthickness.

In some embodiments, the atmosphere in process (ii) is in the reactionspace used in process (i), wherein process (i) and process (ii) can beperformed continuously. Alternatively, in other embodiments, theatmosphere in process (ii) is in another reaction space different fromthe reaction space used in process (i).

In some embodiments, process (ii) comprises: feeding Ar and/or He to theatmosphere without feeding hydrogen, oxygen, and nitrogen; and applyingelectromagnetic energy to the atmosphere in a manner generating Arand/or He plasma. As a plasma, although a capacitively coupled plasmamay typically be used, inductively coupled plasma, remote plasma, aplasma generated by RF power, a plasma generated by microwaves, etc. canalso be used. In some embodiments, a He plasma is most effective. The Arand/or He plasma can reduce thermally unstable hydrogen-relatedfractions such as methyl and/or methylene fractions from the amorphouscarbon polymer film (e.g., by further promoting polymerization, ratherthan by separating the fractions), thereby increasing thermal stabilityof the film.

In some embodiments, RF power is in a range of 0.06 W/cm² to 0.96 W/cm²per unit area of the substrate, and a duration of process (ii) is in arange of 2 seconds to 300 seconds, so that the plasma treatment caneffectively reform the amorphous carbon polymer film.

In some embodiments, the plasma treatment (the reformation process) canbe conducted under conditions described below.

As a reforming gas for the plasma treatment, Ar and/or He gas is used asa primary gas. Substantially no precursor nor reactant is fed to thereaction space while conducting the reformation process for mosteffective treatment; however, the atmosphere of the reaction space maybe contaminated by impurities or unintended components such as residualgas left in the atmosphere even after purging and/or gas released fromthe film as a result of the plasma treatment. Gas other than Ar or Hemay be present in the atmosphere of the reaction space as long as theatmosphere is substantially devoid of hydrogen, oxygen, and nitrogen.These elements typically interfere with reforming reaction by the Arand/or He plasma treatment. For example, if H₂ is added to the reactionspace during the reformation process, the amorphous carbon polymer filmmay be ashed. By using substantially solely Ar and/or He, the thermalstability of the amorphous carbon polymer film can dramatically beimproved. In some embodiments, a gas volume ratio of Ar/He in thereaction space is in a range of 1/0 to 0/1 during the reformationprocess.

As for the reformation temperature, when the treatment is carried out insitu typically in a cyclic manner, preferably, the temperature iscompatible with the flowable deposition (e.g., <125° C.). When thetreatment is applied ex situ in a different chamber or on none-flowablefilm, there is no restriction imposed on the temperature (e.g., <800°C.).

As for RF power for the reformation process, in some embodiments, an RFpower of 50-800 W, preferably 200-600 W, is applied to the electrodes asmeasured for a 300-mm wafer (RF power can be calculated for a differentsize wafer using RF power (W/cm²) calculated per unit area of a 300-mmwafer).

As for the duration of the reformation process, in some embodiments, theplasma treatment (a period of applying RF power) is continued for 2-300seconds, preferably 10-30 seconds.

In some embodiments, the substrate has a patterned recess or step on itssurface on which the amorphous carbon polymer film is deposited,although the reformation process is also applicable to the amorphouscarbon polymer film deposited on a planar surface as a blanket carbonpolymer film.

The embodiments will be explained with respect to the drawings by way ofexample and without any limitation.

FIG. 5 is a chart illustrating the sequence of processes of filmformation according to an embodiment of the present invention, wherein acell in gray represents an ON state whereas a cell in white representsan OFF state, and the width of each column does not represent durationof each process. By this reforming technique, thermal stability of anamorphous carbon polymer film can significantly be improved, and alsodry etch rate of the film can significantly be lowered.

This process sequence comprises a deposition process (“Feed”→“Purge”→“RFPulse-1” (plasma polymerization)→“Purge”), and a plasma treatmentprocess (“Stabilize”→“RF Pulse-2” (plasma reformation)→“Purge”). Theplasma polymerization process comprises depositing an amorphous carbonpolymer film on surfaces of a step on a substrate by PEALD using a Si-and metal-free, C-containing precursor and a plasma-generating gas whichgenerates a plasma by applying RF power (RF) between two electrodesbetween which the substrate is placed in parallel to the two electrodes,wherein RF power is applied in each monolayer deposition cycle of PEALD,wherein the plasma-generating gas and the carrier gas flow continuouslyand function also as a purging gas during “Purge” after “Feed” andduring “Purge” after “RF Pulse-1”.

The deposition process is a PEALD process, one cycle of which forforming a monolayer may be repeated at q times until a desired thicknessof the amorphous carbon polymer film is obtained before starting theplasma treatment process, wherein q is an integer of 1 to 50 (preferably3 to 35), depending on the intended use of the film, etc., so as todeposit the amorphous carbon polymer film having a thickness of 1 nm to15 nm (preferably 5 nm to 10 nm) before starting the plasma treatmentprocess.

Next, the plasma treatment process begins, which comprises feeding areforming gas (Ar and/or He) to the reaction space (“Stabilize”) whichis excited by RF power (RF) to generate a plasma and reform theamorphous carbon polymer film without further depositing a polymer film(“RF Pulse-2”), followed by purging (“Purge”), wherein the reforming gasis fed continuously to the reaction space throughout the plasmatreatment process. For example, RF power for the plasma reformation isin a range of 50 W to 1000 W (preferably 150 W to 500 W), which is equalto or higher than that used for the plasma polymerization, under apressure of 100 Pa to 600 Pa (preferably 200 Pa to 400 Pa) which islower than (e.g., less than half of) that used for the plasmapolymerization. Typically, by the plasma treatment, the thickness of thefilm may be substantially unchanged or may be slightly decreased (e.g.,more than 0%, less than 10%, more typically less than 5%).

In some embodiments, throughout the entire processes, the carrier gas isfed continuously to the reaction space in a range of 0 sccm to 2000 sccm(preferably 100 sccm to 500 sccm), for example. Also, the temperature ofthe processes may be in a range of −50° C. to 175° C. (preferably 35° C.to 150° C.).

The plasma-generating gas in the deposition process and the reforminggas in the plasma treatment process can be the same or different, e.g.,both can be Ar and/or He.

Further, as necessary, the deposition process and the plasma treatmentprocess are repeated at p times until the amorphous carbon polymer filmhaving a desired thickness is obtained, wherein p is an integer of 1 to120 (preferably 3 to 24), depending on the intended use of the film,etc., so as to deposit the final amorphous carbon polymer film having athickness of 5 nm to 1000 nm (preferably 20 nm to 200 nm).

The continuous flow of the carrier gas can be accomplished using aflow-pass system (FPS) wherein a carrier gas line is provided with adetour line having a precursor reservoir (bottle), and the main line andthe detour line are switched, wherein when only a carrier gas isintended to be fed to a reaction chamber, the detour line is closed,whereas when both the carrier gas and a precursor gas are intended to befed to the reaction chamber, the main line is closed and the carrier gasflows through the detour line and flows out from the bottle togetherwith the precursor gas. In this way, the carrier gas can continuouslyflow into the reaction chamber, and can carry the precursor gas inpulses by switching between the main line and the detour line. FIG. 1Billustrates a precursor supply system using a flow-pass system (FPS)according to an embodiment of the present invention (black valvesindicate that the valves are closed). As shown in (a) in FIG. 1B, whenfeeding a precursor to a reaction chamber (not shown), first, a carriergas such as Ar (or He) flows through a gas line with valves b and c, andthen enters a bottle (reservoir) 20. The carrier gas flows out from thebottle 20 while carrying a precursor gas in an amount corresponding to avapor pressure inside the bottle 20, and flows through a gas line withvalves f and e, and is then fed to the reaction chamber together withthe precursor. In the above, valves a and d are closed. When feedingonly the carrier gas (noble gas) to the reaction chamber, as shown in(b) in FIG. 1B, the carrier gas flows through the gas line with thevalve a while bypassing the bottle 20. In the above, valves b, c, d, e,and f are closed.

The process cycle can be performed using any suitable apparatusincluding an apparatus illustrated in FIG. 1A, for example. FIG. 1A is aschematic view of a PEALD apparatus, desirably in conjunction withcontrols programmed to conduct the sequences described below, usable insome embodiments of the present invention. In this figure, by providinga pair of electrically conductive flat-plate electrodes 4, 2 in paralleland facing each other in the interior 11 (reaction zone) of a reactionchamber 3, applying HRF power (13.56 MHz or 27 MHz) 25 to one side, andelectrically grounding the other side 12, a plasma is excited betweenthe electrodes. A temperature regulator is provided in a lower stage 2(the lower electrode), and a temperature of a substrate 1 placed thereonis kept constant at a given temperature. The upper electrode 4 serves asa shower plate as well, and reactant gas and/or dilution gas, if any,and precursor gas are introduced into the reaction chamber 3 through agas line 21 and a gas line 22, respectively, and through the showerplate 4. Additionally, in the reaction chamber 3, a circular duct 13with an exhaust line 7 is provided, through which gas in the interior 11of the reaction chamber 3 is exhausted. Additionally, a transfer chamber5 disposed below the reaction chamber 3 is provided with a seal gas line24 to introduce seal gas into the interior 11 of the reaction chamber 3via the interior 16 (transfer zone) of the transfer chamber 5 wherein aseparation plate 14 for separating the reaction zone and the transferzone is provided (a gate valve through which a wafer is transferred intoor from the transfer chamber 5 is omitted from this figure). Thetransfer chamber is also provided with an exhaust line 6. In someembodiments, the deposition of multi-element film and surface treatmentare performed in the same reaction space, so that all the steps cancontinuously be conducted without exposing the substrate to air or otheroxygen-containing atmosphere.

In some embodiments, in the apparatus depicted in FIG. 1A, the system ofswitching flow of an inactive gas and flow of a precursor gasillustrated in FIG. 1B (described earlier) can be used to introduce theprecursor gas in pulses without substantially fluctuating pressure ofthe reaction chamber.

In some embodiments, a dual chamber reactor (two sections orcompartments for processing wafers disposed close to each other) can beused, wherein a reactant gas and a noble gas can be supplied through ashared line whereas a precursor gas is supplied through unshared lines.

The film having filling capability can be applied to varioussemiconductor devices including, but not limited to, cell isolation in3D cross point memory devices, self-aligned Via, dummy gate (replacementof current poly Si), reverse tone patterning, PC RAM isolation, cut hardmask, and DRAM storage node contact (SNC) isolation.

EXAMPLES

In the following examples where conditions and/or structures are notspecified, the skilled artisan in the art can readily provide suchconditions and/or structures, in view of the present disclosure, as amatter of routine experimentation. A skilled artisan will appreciatethat the apparatus used in the examples included one or morecontroller(s) (not shown) programmed or otherwise configured to causethe deposition and reactor cleaning processes described elsewhere hereinto be conducted. The controller(s) were communicated with the variouspower sources, heating systems, pumps, robotics, and gas flowcontrollers or valves of the reactor, as will be appreciated by theskilled artisan.

Example 1

An amorphous carbon polymer film was deposited on a Si substrate (havinga diameter of 300 mm and a thickness of 0.7 mm) by PEALD-like processwhich is defined in U.S. patent application Ser. No. 16/026,711, eachdeposition cycle of which was conducted as the deposition processillustrated in FIG. 5 under the conditions shown in Table 1 below usingthe apparatus illustrated in FIG. 1A and a gas supply system (FPS)illustrated in FIG. 1B. As the reformation process as illustrated inFIG. 5 was conducted after every 12 cycles of the PEALD-like process(q=12), under the conditions shown in Table 2 below, which was conductedin the same reaction chamber as in the deposition process. The abovecombined cycles were repeated 24 times (p=24). The total (final)thickness of the film was roughly 100 nm.

TABLE 1 Temp. setting SUS temp (° C.). 68 SHD temp (° C.) 75 Wall temp(° C.) 75 BLT temp (° C.) RT Depo Pressure (Pa) 1100 Gap (mm) 14 Feedtime (s) 0.4 Purge (s) 0.1 RF time (s) 1.5 Purge (s) 0.1 RF power (W)175 Precursor cyclopentene Carrier He Carrier flow (slm) 0.1 Dry He(slm) 0.2 Seal He (slm) 0.1 (numbers are approximate)

TABLE 2 No reformation Reformation with Reformation with (“STD”) Ar(“Ar”) He (“He”) Cycle frequency — Every 5 nm Every 5 nm Reforming gas —Ar only He only Pressure — 300 Pa 350 Pa RF power — 300 W 175 W Durationof RF — 30 sec. 30 sec. (numbers are approximate)

In the reformation process, the amorphous carbon polymer film wasexposed to an Ar plasma (“Ar”) or a He plasma (“He”) every time once thefilm thickness increased by about 5-nm increments (a ratio of depositioncycle to reformation cycle was 12). As a comparative example, noreformation process was conducted in “STD”, i.e., the amorphous carbonpolymer film was deposited without the reformation process. Each of theresultant amorphous carbon polymer films (three “STD” films, one “Ar”film, and two “He” films) was annealed under one of the conditions shownin Table 3 below, in order to evaluate thermal stability of each film(film shrinkage after anneal).

TABLE 3 Anneal 1 Anneal 2 Anneal 3 (N2 200 C./ (N2 300 C./ (Vac 300 C./30 min) 60 min) 80 min) Atmosphere N₂ N₂ No gas flow Pressure 400 Pa 400Pa 3 Pa Temperature 200° C. 300° C. 300° C. Duration 30 min. 60 min. 80min. (numbers are approximate)

The results are shown in FIG. 2. FIG. 2 is a graph showing shrinkage ofthe amorphous carbon films without plasma treatment (“STD”), with the Arplasma treatment (“Ar”), and with the He plasma treatment (“He”) afterannealing. As shown in FIG. 2, the amorphous carbon polymer films formedusing the Ar or He plasma cyclic treatment showed surprisingly lowshrinkage in the various annealing conditions, indicating high thermalstability, as compared with the amorphous carbon polymer films formedwithout plasma cyclic treatment.

FIG. 3 shows Fourier Transform Infrared (FTIR) spectrums of theamorphous carbon films without plasma treatment (“STD”), with the Arplasma treatment (“Ar”), and with the He plasma treatment (“He”) (beforebeing subjected to the annealing). As shown in FIG. 3, the amorphouscarbon polymer films formed using the Ar or He plasma cyclic treatmentshowed a significant decrease of H-related peaks, wherein the Ar or Heplasma cyclic treatment reduced thermally unstable methyl and methylenefractions, as compared with the amorphous carbon polymer films formedwithout plasma cyclic treatment.

Example 2

Amorphous carbon polymer films (“STD”, “Ar”, and “He”) were formed inthe same manner as in Example 1, and properties of the resultantamorphous carbon polymer films were evaluated. The results are shown inTable 4 below.

TABLE 4 STD-film Ar-film He-film RI  1.54 1.53 1.63 Water Contact Angle[°] (25° C.) 66.1 78.9 60.6 Stress [MPa] ^(~)0   −120 −440 RBS [%] C51.0 51.0 54.0 H 46.0 47.0 39.0 O  3.0 2.0 7.0 N ND ND ND Thermal  50°C./30 min 0  — — shrinkage [%] 125° C./30 min 10-20 — — 200° C./30 min17.6 7.1 0.6 300° C./30 min 35.4 5.4 0 (numbers are approximate)

As shown in Table 4, the thermal shrinkage of the amorphous carbonpolymer film with the He plasma treatment (“He-film”) was remarkablylower than that of the amorphous carbon polymer film without plasmatreatment (“STD-film”), wherein the thermal shrinkage of the He-film wassubstantially zero, indicating that the thermal stability of the He-filmwas excellent. In addition to the results shown in the FTIR of FIG. 3,considering the data in Table 4 showing that the He plasma treatmentaffected the properties of the film in a manner that RI of the He-filmwas higher than that of the STD-film, the water contact angle of theHe-film was lower than that of the STD-film, the stress of the He-filmwas highly compressive as compared with that of the STD-film, and the Ccontent of the He-film was higher than that of the STD-film whereas theH content of the H-film was lower than that of the STD-film, the Heplasma treatment was likely to have promoted further polymerization ofthe film matrix, thereby reducing thermally unstable hydrogen-relatedfractions such as methyl and/or methylene fractions from the amorphouscarbon polymer film, and reducing hydrogen bonds at the surface. Itshould be noted that oxygen atoms were detected in each film, and it maybe because the films were exposed to air after the substrates were takenout from the reaction chamber.

Interestingly, according to the data in the FTIR of FIG. 3 and datashown in Table 4 as analyzed in a manner similar to that in the Heplasma treatment, in the Ar plasma treatment, polymerization appears tobe less progressed than in the He plasma treatment, whereinpolymerization progressed to a certain degree, reducing hydrogen bondsin the film matrix, whereas hydrogen bonds on the surface increased(more hydrogenation on the surface). Thus, although the composition ofthe Ar-film appears to be substantially the same as that of theSTD-film, the chemical structures of the films associated with hydrogenare considered to be different, wherein the Ar-film is more thermallystable than the STD-film but is less thermally stable than the He-film.In some embodiments, Ar-films and He-films are a hydrogenated amorphouscarbon polymer having a composition constituted by more than 50% ofcarbon atoms and more than 35% but less than 50% of hydrogen atoms (asmeasured using, e.g., Rutherford backscattering Spectrometry (RBS)),wherein thermal shrinkage is less than 10% (preferably less than 5%) asmeasured when being placed in an atmosphere of N₂ under a pressure of400 Pa at a temperature of 300° C. for 30 minutes as reference/standardconditions.

Example 3

An amorphous carbon polymer film was deposited on a Si substrate (havinga diameter of 300 mm and a thickness of 0.7 mm) with a SiO liner havingnarrow/deep trenches with an opening of approximately 50 nm, which had adepth of approximately 90 nm (an aspect ratio was approximately 1.8),and narrow/shallow trenches with an opening of approximately 5 to 10 nm,which had a depth of approximately 90 nm, in the same manner as in thereformation with He in Example 1 except that the He plasma treatment wasconducted after approximately every 10 nm (24 cycles of deposition) asmeasured on a planar surface (as blanket deposition).

FIG. 4 shows a STEM photograph of a cross-sectional view of the trenchessubjected to the gap-fill process (bottom-up deposition) with the Heplasma treatment, wherein arrows show slightly darker interfacesindicative of the He plasma treatment. Although the darker interfacesare indicative of the He plasma treatment, they do not represent layersreformed by the He plasma treatment, i.e., the reformation effectpenetrates beyond the interfaces and reaches deeper portions of layersbetween the adjacent interfaces. In this example, the SiO liner was usedin order to reduce the CD of the structure, and the SiO liner was theonly layer which was conformal. As indicated by the arrows, although theHe plasma treatment was cyclically conducted after every approximately10 nm as measured on a planar surface, in the trenches, the viscousliquid-like behavior of amorphous carbon polymer is observed wherein thedistance between the adjacent interfaces is significantly larger in thetrenches than above the trenches. Interestingly, the distance betweenthe adjacent interfaces gradually increases from the bottom as the filmgrowth progresses and becomes the largest in the middle of the trenchesin depth, and then gradually decreases toward the top of the trenches,indicating that the amorphous carbon polymer behaved as viscous liquid.Further, the film filled faster in the narrow trenches than in the widertrenches, indicating volumetric growth. Since the He plasma treatmentformed darker interfaces which function as deposition markers, the abovebehavior can readily be observed in the STEM photograph. Typically, theplasma reformation effect reaches to a depth of about 10 nm, forexample, and thus, inside the trenches where the distance between theadjacent interfaces is more than 10 nm, the plasma reformation effectcan be considered insufficient; however, it appears that portions offilm, which are temporarily deposited on the top and the sidewall oftrenches and exposed to an Ar/He plasma, move downward to fill thetrenches, and thus, it is expected that each amorphous carbon polymerlayer may be relatively homogenous even if their thickness is over 10 nminside the trenches (interfaces adjacent to the sidewalls and the top ofthe trenches are not as clear as those away from the sidewall and thetop).

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. Therefore, it should be clearly understood thatthe forms of the present invention are illustrative only and are notintended to limit the scope of the present invention.

I claim:
 1. A method for reforming an amorphous carbon film as part of adeposition process thereof, comprising processes of: (i) depositing anamorphous carbon film using a silicon- and metal-free precursor on asubstrate in a reaction space until a thickness of the amorphous carbonfilm reaches a predetermined thickness, and then stopping the depositionprocess; and (ii) annealing the amorphous carbon film by exposing theamorphous carbon film to an Ar and/or He plasma in an atmospheresubstantially devoid of hydrogen, oxygen, and nitrogen, wherein process(ii) comprises feeding Ar and/or He to the atmosphere without feedinghydrogen, oxygen, and nitrogen; and applying RF power to the atmospherein a manner generating the Ar and/or He plasma, and wherein process (i)is conducted by plasma-enhanced atomic layer deposition (PEALD).
 2. Themethod according to claim 1, wherein processes (i) and (ii) are repeatedmultiple times until a thickness of the amorphous carbon film reaches adesired final thickness.
 3. The method according to claim 1, wherein thepredetermined thickness in process (i) is a monolayer thickness or morebut 10 nm or less.
 4. The method according to claim 1, wherein theatmosphere in process (ii) is in the reaction space used in process (i).5. The method according to claim 1, wherein the atmosphere in process(ii) is in another reaction space different from the reaction space usedin process (i).
 6. The method according to claim 1, wherein RF power isin a range of 0.06 W/cm² to 0.96 W/cm² per unit area of the substrate,and a duration of process (ii) is in a range of 2 seconds to 300seconds.
 7. The method according to claim 1, wherein the substrate has apatterned recess or step on its surface on which the amorphous carbonfilm is deposited.